The study of the synthesis of isethionate (2-hydroxyethanesulfonate) and taurine will be contained. The sulfur sources will be Na235S, 35S-cysteine, and outer-35S-thiosulfate. The carbon sources will be 14C-labelled glucoses and acetyl-14C-CoA. These experiments are planned on the recent evidence that no direct pathway from taurine to isethionate exists, but that there is a pathway through sulfide to isethionate. Because of the impermeability of thiosulfate and acetylCoA into the squid giant axon, these experiments will be performed on homogenates or defined fractions of squid optic ganglia. The 14C-35S double labelled isethionate ss formed will be assayed for each isotope separately by a new method developed in this laboratory. Since the pathways involved are contributing to the anion content of cephalopod nerve cells, we will perturb the pathway by varying anion and cation concentrations, and will interpret the results in terms of allosteric controls of the enzymes of sulfur metabolism. We will continue to search for the natural substrate for DFPase in the belief that this enzyme is involved in the hydrolysis of an isethionate precursor, and will examine the properties of rhodanese that may be related to the transfer of sulfer from thiosulfate to acetylCoA to form a -C-C-S- precursor of isethionate.